Publication No. 16-09-044 (July 2016) Page i Dioxins, Furans, and Dioxin-Like PCB Congeners: Ecological Risk Calculation Methodology for Upland Soil Implementation Memorandum No. 13 Date: July 12, 2016 To: Interested Persons From: Jeff Johnston, Manager Information & Policy Section Toxics Cleanup Program Contact: Arthur Buchan, Toxicologist, [email protected], 360.407.7146 Policy & Technical Support Unit, Toxics Cleanup Program Attachments: None Accommodation Requests: To request ADA accommodation including materials in a format for the visually impaired, call Ecology’s Toxics Cleanup Program at 360-407-7170. Persons with impaired hearing may call Washington Relay Service at 711. Persons with speech disability may call TTY at 877-833-6341.
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Publication No. 16-09-044 (July 2016) Page i
Dioxins, Furans, and Dioxin-Like PCB Congeners: Ecological Risk Calculation Methodology for Upland Soil
Implementation Memorandum No. 13
Date: July 12, 2016
To: Interested Persons
From: Jeff Johnston, Manager
Information & Policy Section
Toxics Cleanup Program
Contact: Arthur Buchan, Toxicologist, [email protected], 360.407.7146
Policy & Technical Support Unit, Toxics Cleanup Program
Attachments: None
Accommodation Requests: To request ADA accommodation including materials in a format for
the visually impaired, call Ecology’s Toxics Cleanup Program at 360-407-7170. Persons with
impaired hearing may call Washington Relay Service at 711. Persons with speech disability may
2.4 Screening Levels for Dioxins, Furans, and PCBs ................................................. 5
2.5 Summary of TEQ Methodology............................................................................. 5
2.6 TEQ Methodology for Ecological Risk Assessment .............................................. 7
3.0 General Procedures for Determining Compliance for Dioxins, Furans, and PCBs using the TEE Table Values in WAC 173-340-900 ............................................ 9
4.0 Step-by-Step Procedure for Determining Compliance for Mixtures of Dioxins, Furans, and PCBs Using the TEE Table Values in WAC 173-340-900 and EPA Method 1668 ................................................................................................................ 11
5.0 How do I determine if dioxins, furans or PCBs are contaminants of ecological concern? ...................................................................................................................... 15
6.0 What method do I use to analyze PCBs? ........................................................... 17
7.0 Step-by-Step Procedure for Determining Compliance for Mixtures of PCBs Using the Tables in WAC 173-340-900 and EPA Method 8082 or EPA Method 1668 ...................................................................................................................................... 19
8.0 Step-by-Step Procedure for Calculating Site-Specific Dioxin, Furan, and PCB Ecologically Protective Cleanup Levels and Determining Compliance (When Using Methods other than MTCA Tables 749-2 or Table 749-3) ............................. 21
Washington State Department of Ecology Toxics Cleanup Program Implementation Memo #13
Publication No. 16-09-044 (July 2016) Page iii
List of Tables, Figures, & Equations
Table 1: TEE screening levels for dioxins, furans, and PCBs ......................................... 5
Table 2: PCDD, PCDF, and PCB toxicity equivalency factors for mammals and avians 8
Table 3: General procedures for determining compliance for dioxins, furans, and PCBs using the TEE table values in WAC 173-340-900 ........................................................... 9
Table 4: How to determine if dioxins, furans, or PCBs are contaminants of ecological concern ......................................................................................................................... 15
Figure 1. Chemical structure of PCDDs (dioxins), PCDFs (furans), and dioxin-like PCBs. Numbers by aromatic ring carbons in general structures represent potential chlorine substitutions (USEPA 2008). ............................................................................. 3
Figure 2: Illustration of the toxic response created by any of the 29 dioxin-like congeners (BEC 2012). ................................................................................................... 4
Figure 3: Summary of calculating contaminant levels for use with screening to MTCA Table 749-2 or 749-3. Methods include EPA Method 1613 (USEPA 1994) for Dioxin/Furan analysis, and EPA Methods 1668 (USEPA 2008) and EPA Method 8082 (USEPA 2007) for PCB analysis. .................................................................................. 10
Equation 1: Calculating TEQ concentrations in samples. (Van den Berg et al., 1998) ...................................................................................................................................... 23
Washington State Department of Ecology Toxics Cleanup Program Implementation Memo #13
Publication No. 16-09-044 (July 2016) Page iv
Acronyms
Ah aryl hydrocarbon
CAS Chemical Abstracts Service
DNA deoxyribonucleic acid
EDL estimated detection limit
EQL estimated quantitation limit
KM Kaplan-Meier
MTCA Model Toxics Control Act
PCB polychlorinated biphenyl
PCDD chlorinated dibenzo-p-dioxin
PCDF chlorinated dibenzofuran
PQL practical quantitation limit
QAPP Quality Assurance Project Plan
TCDD 2,3,7,8-Tetrachlorodibenzo-p-dioxin
TCP Toxics Cleanup Program
TEE Terrestrial Ecological Evaluation
TEF toxicity equivalency factor
TEQ toxicity equivalency quotient
USEPA United States Environmental Protection Agency
WAC Washington Administrative Code
Publication No. 16-09-044 (July 2016) Page 1
1.0 Purpose and Applicability
The purpose of this memorandum is to document an interpretation from the Department of
Ecology (Ecology) regarding the different procedures that should be used to calculate site
contaminant concentrations for three types of contaminants when conducting a Terrestrial
Ecological Evaluation under the Model Toxics Control Act (MTCA) (WAC 173-340-7490
through -7494) (Ecology 2007a). The three contaminant types are:
Chlorinated dibenzo-p-dioxins (PCDDs) (2,3,7,8-TCDD is a member of this class);
Chlorinated dibenzofurans (PCDFs); and
Polychlorinated biphenyls (PCBs) (includes both total PCBs and dioxin-like PCBs).
This memorandum specifically pertains to Ecological Risk Assessment and the Terrestrial
Ecological Evaluation (TEE) under MTCA (WAC 173-340-7490 through -7494).
2.0 Background
2.1 Dioxin/Furans
PCDDs and PCDFs (dioxins and furans) are typically present in the environment as complex
mixtures of chemically-related substances (congeners) that differ in the number and location of
chlorine atoms (Ecology, 2007b). There are 210 of these dioxin and furan congeners present in
the environment. The most toxic and best studied congener is 2,3,7,8-Tetrachlorodibenzo-p-
dioxin (TCDD) (Ecology 2007c), which is why TCDD is the standard for comparison in the
methodologies outlined in this memo.
Because dioxin and furan congeners are typically present in the environment as complex
mixtures, scientists developed a toxicity equivalency quotient (TEQ) methodology that evaluates
the toxicity and assesses the risks associated with whole mixtures. With the TEQ method, each
congener is assigned a TEF, or toxicity equivalency factor: the ratio of estimated toxicity for a
particular congener to the toxicity of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) (Ecology
2007c). The TEQ approach is based on the concept that the various dioxin and furan congeners
act through a common biological mechanism involving the aryl hydrocarbon (Ah) receptor.
Note: MTCA’s Terrestrial Ecological Evaluation established separate screening levels for
dioxins and furans in WAC 173-340-900 (Tables 749-2 and 749-3). However, when Table 749-
2 or Table 749-3 is not used, the dioxins and furans should be treated as one mixture for the
purposes of calculating and comparing to cleanup levels.
As a result, there are two processes to calculate site contaminant levels for dioxins and furans:
(1) Source: Van den Berg, et al. (2006) and Van den Berg et al. (1998). The 2005 World Health
Organization re-evaluation of human and mammalian toxicity equivalency factors for dioxins and dioxin-
like compounds. Toxicological Sciences, 2006 93(2), 223-241; doi:10.1093/toxsci/kfl055.
Washington State Department of Ecology Toxics Cleanup Program Implementation Memo #13
Publication No. 16-09-044 (July 2016) Page 9
3.0 General Procedures for Determining Compliance for
Dioxins, Furans, and PCBs using the TEE Table Values in
WAC 173-340-900
Table 3: General procedures for determining compliance for dioxins, furans, and PCBs using the TEE table values in WAC 173-340-900
To Determine Compliance for
Use this Procedure Procedure
No.
Dioxin congeners
Compare the sum of the TEF-adjusted concentrations (TEQ) for the seven (7) dioxin congeners to the appropriate screening level (Table 749-2 or Table 749-3, as appropriate for the site) for “chlorinated dibenzo-p-dioxins (total).”
1
Furan congeners
Compare the TEQ for the ten (10) furan congeners to the appropriate screening level (Table 749-2 or Table 749-3) for “chlorinated dibenzofurans (total).”
2
To Measure Use this Procedure Procedure
No.
Total PCB concentrations using EPA Method 8082
Compare the total Aroclors (no adjustments using TEFs) to the “PCB mixtures (total)” screening level (Table 749-2 or Table 749-3).
3
PCB congeners using EPA Method 1668
Compare the total PCB Congener Analysis (no adjustments using TEFs) to the “PCB mixtures (total)” screening level (Table 749-2 or Table 749-3);
AND
4A
Compare the sum of the TEQs equivalency for the twelve (12) dioxin-like PCB congeners to the appropriate screening level (Table 749-2 or Table 749-3) for “chlorinated dibenzo-p-dioxins (total).”
4B
Mixtures of dioxin, furans and PCBs
Use Procedure 4A (above) to calculate and compare a “PCB mixtures (total)” screening level (Table 749-2 or Table 749-3);
AND
5A
Use Procedures 1, 2, and 4B (above) for each component of the dioxin, furan, and dioxin-like PCB congeners.
5B
Summary:
1. Adjust the concentration of each congener by the appropriate TEF. 2. Sum to calculate a total TEQ concentration (which includes dioxins, furans,
and dioxin-like PCBs). 3. Compare this total TEQ concentration with the screening level (Table 749-2
or Table 749-3) for “chlorinated dibenzo-p-dioxins (total).”
Washington State Department of Ecology Toxics Cleanup Program Implementation Memo #13
Publication No. 16-09-044 (July 2016) Page 10
Figure 3: Summary of calculating contaminant levels for use when comparing screening levels to MTCA Table 749-2 or 749-3. Methods include EPA Method 1613 (USEPA 1994) for Dioxin/Furan analysis, and EPA Methods 1668 (USEPA 2008) and EPA Method 8082 (USEPA 2007) for PCB analysis.
Note: Total Aroclors (USEPA Method 8082) is an acceptable method to determine Total PCB concentrations. However, only PCB Congener
Analyses (EPA Method 1668) should be used to evaluate the 12 dioxin-like PCB congeners at the site.
Screening Levels
Dioxins
USEPA Method 1613: Sum the TEF
Equivalency products of the 7 dioxin congeners
Compare to Screening Level: Chlorinated dibenzo-p-dioxins
(total):
(Table 749-2 or 749-3)
Furans
USEPA Method 1613: Sum the TEF
Equivalency products of the 10
dioxin-like furan congeners
Compare to Screening Level: Chlorinated
dibenzofurans (total):
(Table 749-2 or 749-3)
PCBs
Total PCBs Only
USEPA Method 8082
Compare to Screening Level: PCB Mixtures
(total):
(Table 749-2 or 749-3)
Total PCBs and Dioxin-Like PCBs
USEPA Method 1668
Total PCBs: USEPA Method 1668
Compare to Screening Level: PCB
Mixtures (total):
(Table 749-2 or Table 749-3)
USEPA Method 1668: Sum the TEF Equivalency products of the 12 dioxin-
like PCB congeners
Compare to Screening Level: Chlorinated dibenzo-p-dioxins
(total):
(Table 749-2 or 749-3)
OR
+
Washington State Department of Ecology Toxics Cleanup Program Implementation Memo #13
Publication No. 16-09-044 (July 2016) Page 11
4.0 Step-by-Step Procedure for Determining Compliance for
Mixtures of Dioxins, Furans, and PCBs Using the TEE Table
Values in WAC 173-340-900 and EPA Method 1668
Overview:
When establishing and determining compliance using the screening level tables in WAC 173-
340-900, mixtures of dioxins should be considered a single hazardous substance, mixtures of
furans should be considered another separate single hazardous substance, and mixtures of PCBs
shall be considered a third separate single hazardous substance.
Which screening levels should be used to determine compliance?
Use the Simplified TEE screening levels (MTCA Table 749-2) only at sites where it
has been determined that a Simplified TEE (WAC 173-340-7492) will meet the
Ecological Risk Assessment requirements of WAC 173-340.
Use the Site-Specific TEE screening levels (MTCA Table 749-3) at any site.